Synthesis and Crystal Structure of [C 10 N 2 H 10 ] 2 [P 2 Mo 5 O 21 (OH) 2 ]·2H 2 O

The crystal structure of [C 10 N 2 H 10 ] 2 [P 2 Mo 5 O 21 (OH) 2 ] · 2H 2 O, contains the heteropolyanion, [P 2 Mo 5 O 21 (OH) 2 ] 4— , together with diprotonated 4, 4′‐bipyridine. The heteropolyanion is built up from five MoO 6 octahedra sharing four common edges and one common corner, capped by two PO 3 (OH) tetrahedra. The structure is stabilized by hydrogen bonds involving the hydrogen atoms of the 4, 4′‐bipyridine, water molecules and the oxygen atoms of the pentamolybdatobisphosphate. This is the first example that this kind of cluster could be isolated in the presence of a poly‐functional aromatic molecule ion. Crystal data: triclinic, P1¯ (No. 2), a = 9.983(2)Å, b = 11.269(2)Å, c = 17.604(4)Å, α = 73.50(3)°, β = 84.07(3)°, γ = 67.96(3)°; V = 1760.0(6)Å 3 ; Z = 2; R 1 = 0.037 and w R 2 = 0.081, for 9138 reflections [I > 2σ(I)].